1. Field of the Invention
This invention relates to a planar positioning device in which a displacement magnifying device, comprising a displacement magnifying mechanism and an actuator for driving a stage, is located at right angles to an X-axis and Y-axis, and to a planar positioning device, having a high-precision resolution of sub-nanometer order in the same plane and configured to perform positioning control with quick response, and an inspection device provided with the same.
2. Description of the Related Art
Conventionally, precision scanning stages used in manufacturing and inspection processes for scanning probe microscopes, electron microscopes, semiconductors, and liquid crystals require performance for accurate scanning operation in an angular range of hundreds of micrometers with sub-nanometer positioning accuracy in a plane defined by orthogonal X- and Y-axes. Presently, in a scanning probe microscope, for example, a probe of silicon or the like is used to scan the surface of a sample. To this end, an XYZ-stage is put to practical use in nanometer-order observation. The XYZ-stage is obtained by combining a scanning stage that moves in a 100-μm-square XY-plane with a Z-axis stage for height adjustment of about 5 μm. In the existing state, however, it is technically very difficult to quickly scan the stage with sub-nanometer accuracy, and this scanning, especially if confined to the same plane, is not realized yet.
Even at this moment in time, an XY-stage, which is driven directly by stacked piezoelectric elements, can obtain nanometer-order positioning accuracy. It is very difficult, however, to steadily obtain nanometer-order positioning accuracy with high-speed scanning capability for an angular range of hundreds of micrometers or more.
One reason for this is that no-load extension of each stacked piezoelectric element is very small, adjusted to about 1/1,000 of the natural length of laminated layers. In order to cover the operating range of hundreds of micrometers by means of the piezoelectric elements themselves, two piezoelectric elements having a lamination thickness of hundreds of millimeters must be arranged at right angles to each other, even if the portable mass load is small. Actually, however, it is impossible to transmit elongations of the stacked piezoelectric elements as long as hundreds of millimeters directly to the XY-stage, on the basis of practical use.
To overcome this, various scanning stages are proposed that comprise a displacement magnifying mechanism configured to magnify displacement (or extension) of stacked piezoelectric elements. In general, however, a mechanism for magnifying displacement reduces the rigidity of the stage as the displacement amount increases, possibly resulting in a reduction in the resonant frequency of the stage itself that influences the control performance.
The displacement magnifying mechanism comprises actuators arranged on an X-axis and Y-axis, individually. The displacement magnifying mechanism produces such actions as a rotary action (rotary action around a θ-axis) that cannot be controlled by means of the actuators, as well as accurate actions parallel to the X-axis and Y-axis by the actuators. Thus, the displacement magnifying mechanism hinders accurate nanometer-level positioning.
On the other hand, there is proposed a technique for magnifying displacement of stacked piezoelectric elements without reducing the rigidity of a stage (e.g., Jpn. Pat. Appln. KOKAI Publication No. 2005-261167 (Japanese Patent No. 3612670) and Jpn. Pat. Appln. KOKAI Publication No. 2007-166714).
According to a device disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2005-261167, an actuator amplifies a displacement produced by the stacked piezoelectric elements while maintaining high rigidity and outputs an accurate linear motion as a displacement of a mover. Further, a restraining member is located between a link portion and the mover with a viscoelastic material therebetween. A high-peak amplitude that is produced at a resonant frequency by the actuator is efficiently attenuated and reduced by the restraining member, whereby the control performance of the actuator is improved.
An actuator proposed in Jpn. Pat. Appln. KOKAI Publication No. 2007-166714 comprises a displacement magnifying mechanism that increases a magnified displacement amount while maintaining a high resonant frequency. This displacement magnifying mechanism comprises a supporting portion and a pair of parallel links. The supporting portion is opposed to a movable portion with a gap therebetween. The parallel links individually connect the supporting portion and movable portion and is configured to be elastically deformed as a piezoelectric element is displaced. The piezoelectric element is mounted on one of the parallel links. The other of the parallel links is formed of a leaf spring. The displacement of the piezoelectric element is magnified by a parallel link that comprises a lever structure, elastic hinge, and beam, and transferred to outside the parallel link.
In transmitting an elongation of a stacked piezoelectric element directly to a stage used in a scanning probe microscope or the like, for example, accurate positioning operation can be achieved in a plane defined by an X-axis and Y-axis by the elongation of the stacked piezoelectric element within a small displacement region. In a large operating region, however, actions along the X-axis and Y-axis interfere with each other, that is, one of the axes applies a moment to the other, whereupon rotation around the θ-axis is produced along with their respective translational motions. Thus, bending moment is also produced as stress in the stacked piezoelectric element itself, thereby causing translational motions that are accompanied by rotation around a Z-axis (θ-axis) perpendicular to an XY-plane. Since the stage has neither a function to suppress or correct the action around the Z-axis nor necessary design flexibility for compensation, accurate positioning in the XY-plane is impeded, so that the scanning operation itself cannot be easily controlled.
If the stage that combines two orthogonal actuators with the displacement magnifying mechanism described in Patent Document 2 is used for scanning in the XY-plane, the respective motions of the actuators are restricted unless an appropriate support structure is provided for the stage. Accordingly, the stage is caused to rotate around the Z-axis by interference between the X-axis and Y-axis. Thus, it is difficult to construct a mechanism for quick and precise positioning in the same XY-plane.